The invention is related to an optical transmitter-receiver module, i.e. a module or assembly capable of both transmitting and receiving optical signals, i.e. signals modulated on light.
There is today a need for combined optical transmitters/receivers or transceivers. There is a particular interest in arranging multiple transmitters and receivers in the same array device. Then it may be advantageous either if the transmitter and the receiver can be located alternatingly or if the transmitter and the receiver can be multiplexed on the same fiber. A possible method is to monolithically integrate all these functions on one indium phosphide chip. However, it results in both a complicated simultaneous processing and difficulties associated with optical and electric crosstalk. Another method comprises the use of separate transmitter and receiver chips and arranging optical waveguides for conducting the light to and from the respective chips. The disadvantage of this method is that the substrate in which the waveguides are formed will be large and costly since the bends required in the waveguides have to be made rather large and thus the waveguides are area-consuming. The considerable space required by bends of waveguides is apparent from e.g U.S. Pat. No. 5,064,263 which discloses a receiver module for receiving a plurality of wavelengths on a single fiber.
It is an object of the invention to provide an optical receiver and transmitter module which is the type chips mounted on a substrate and which can be made to have a small total area.
It is another object of the invention to provide an optical receiver and transmitter module which has a minimum of bends in waveguides between component chips and an edge of the module.
The problem to be solved by the invention is how to arrange the waveguides in or on an optical receiver and transmitter module so that the module has a small total area and so that the waveguides have as few and/or as small bends as possible.
An optical receiver and transmitter module comprises a substrate, a receiver or detector unit such as a semiconductor chip, and a transmitter or laser unit which can also be semiconductor chip. The units or components are preferably the array type and are mounted behind each other on the surface of the substrate having their front surfaces on which their optical interface surface are located all facing in the same direction, towards a connector edge of the substrate. Optical waveguides extend from an edge of the substrate up to the active surfaces of the receiver and transmitter chips. The waveguides extending to a rear one of the units pass in grooves in the bottom side of the other one of the units. This design allows a quite straight configuration of the waveguides. Since no space on the substrate is required for bends of the waveguides the substrate can be made with minimum dimensions.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the methods, processes, instrumentalities and combinations particularly pointed out in the appended claims.